Horniday 5.56TAP is in a red box marked Tactical Application Police , not for use in .223 chambers.

There are different chamber reamers currently in use today. A barrel with a "Wylde" chamber was designed to handle NATO pressure loads while delivering better accuracy than a NATO chamber. The Noveske Match Mod O chamber is designed to offer 100% reliability while retaining maximum possible accuracy. The chamber body is slightly larger than the 5.56mm NATO minimum, but within the 5.56 NATO tollerance. the throat is redesigned for proper bullet alignment with the axis of the bore. This chamber was developed to fire MK262 Mod 1 on AUTO in hot enviroments.

There are two cartridges with a "heavy" bullet loaded to 5.56mm NATO pressure specs one is Horniday 5.56 TAP the other is Black Hills MK262.

Black Hills MK262 ammo (BC= .340) muzzle velocity is

Colt 14.5in barrel 2628

Colt 16in barrel 2712

Colt 20 in barrel 2830

Horniday 75 TAP5.56 T2(BC=.352) muzzle velocity is

Colt 14.5in barrel 2627

Colt 16 in barrel 2713

Colt 20 in barrel 2821

The 5.56-mm ball M855 (A059) cartridge has a gilding, metal-jacketed, lead alloy core bullet with a steel penetrator. The primer and case are waterproof. The ammunition is linked by a disintegrating metallic split-linked belt for firing from the ammunition box. In an emergency, the M855 round can also be loaded and fired from the M16 20or 30-round magazine. It is identified by a green tip, has a projectile weight of 62 grains, and is 2.3 cm long. This is the NATO standard round. It is effective against personnel and light materials, not vehicles.

"Any cartridge that does not have the cross and circle (+) in itsheadstamp is not NATO approved, no matter what the ads say. Real NATOammunition must be manufactured under NATO surveillance and be certified tomeet strict requirements for velocity, chamber and port pressure, barreltime, temperature stability, barrel erosion, waterproofing and othercharacteristics. Furthermore, NATO ammunition must be produced by aspecified facility in a NATO country. Ammunition made by surrogate nationscannot carry the NATO symbol or interchangeability code. An item oftenoverlooked is that M193 Ball 5.56mm ammunition cannot be NATO approved,since the official NATO round is the SS109 (U.S. M855) cartridge.

* Drift for 10 mph wind.M193 Ball ammunition fired in M16A1 rifle with 250 meter battle sight zero.M855 Ball ammunition fired in M16A2 rifle with 300 meter battle sight zero. Because the steel penetrator increases the length and changes theweight distribution of the SS109 bullet, it is suitable for use only inbarrels with a twist of one turn in nine inches or faster.

The SS109 5.56mm NATO cartridge is a second generation intermediate power round developed with 1970's technology. It is significantly more powerful and effective than the U. S. M193 5.56mm ball round originally used with the M16 rifle. The new SS109 cartridge propels a heavier 62-grain semi-armor piercing projectile at an initial velocity of 3,050 fps (924 mps).18 The improved projectile contains a 10-grain .182 caliber hardened steel penetrator that ensures penetration at longer ranges. Total cartridge length and weight are 2.26 inches and 182.0 grains, respectively. The increased length and weight of the new SS109 projectile requires a faster rifling twist of one turn in seven inches to fully stabilize the new projectile in flight.19 The predecessor M193 5.56mm, which used a projectile weighting only 55 grains, was only marginally stabilized with a slower rifling twist of one turn in twelve inches. The new projectile can penetrate the standard NATO 3.45mm steel plate up to a range of 640 meters (704 yds) and one side of the U. S. steel helmet up to a range of 1,300 meters (1430 yds).20 In tests of barrier and fortification penetration however, the steel penetrator of the SS109 could not pierce any of the test building blocks. http://ammo.ar15.com/ammo/project/hist_m855.html

"Always do the right thing, just because it is the right thing to do".Bobby Paul DohertyTexas Ranger

None,Unless you're speaking of a rifle chambered for the .223 Remington. Go to the Ruger website and get a manual for the mini14. There you will see either cartridge is acceptable. The military brass is made slighty thicker and therefore a slightly longer head space is required. There are some bolt .223's that say .223 Remington and those should just cycle .223 ammo. Although who would own a blt .223? lol. The mini14 says just .223 on it. Reloading data is identicle for either cartridge, the "hotter" that folks mention is because there is a slight increase in breech pressure due to the military brass having more yield strength due to it's thickness. I have reloaded all my life and intentionally overloaded (minimally) to see the different trade marks of over pressure and I seriously doubt in any .223 you would see any difference running 5.56CHill

most of the warning, around the 70's, were directed towards guns using softer actions than normal, a few Sakos as I recall were ruined. While actions are usually harder, some gun barrels can run "soft" and stretch in the chamber area. Military brass usually has less internal case capacity due do a thicker web, so the same powder charge develops higher pressure as mentioned above. Never could understand why someone would want to run lesser quality military thru a high quality sporter. 223 will easily blow primers when some of the faster powders are used to hotrod, h335,tac etc with a density that doesn't fill the case in either of the military or commercail cases

The only comment I have is the 5.56 through a Remington bolt gun or a TC Contender barrel is no problem.But, based on military ammo I've used, a commercial .223 is a far better choice for hunting. I have no problem with FMJ for predators to preserve the pelt. It's just that commercial .223 really shoots great versus the various various tipped mil stuff I have.

A lot of it has to do with 5.56mm chamber pressure being more than the commercial .223. Military internal dimensions are different. Some external specs are different. You will always here it is no issue firing .223 in 5.56mm chambers, but "unsafe" vice versa.

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